When two substances, such as a powder and a liquid for example, are mixed together and stored in a container for a relatively short period of time, it sometimes happens that their properties are such that the mixture degrades or is otherwise rendered unusable for its intended purpose. One example involves dry powder baby formula that is designed to be mixed with water. When separately stored, the powder formula and the water can be kept in a usable condition for a relatively long period of time. When mixed together however, the resulting solution spoils rather quickly and is no longer usable. There is a need therefore for a container which is capable of separately storing two or more substances and of mixing them when desired.
Various known containers and devices were designed to achieve this purpose. However, many of them have disadvantages including high manufacturing costs, complicated structures, one-time use capability only, unreliable operation, difficulty in achieving good mixing results, inconvenient or awkward actuation for causing the substances to mix together, and/or difficulty in cleaning and re-assembly, etc. There is therefore a need for improved devices and methods for storing and mixing substances in order to overcome some or all of the foregoing disadvantages.